1. Field of the Invention
The invention relates to a system for providing a remote subscriber identity card, and more particularly to a system for providing multiple remote subscriber identity cards to a mobile station.
2. Description of the Related Art
Currently, the Global System for Mobile communication (GSM) standard is the most popular standard for mobile phones in the world. The GSM standard, standardized by the European Telecommunication Standards Institute (ETSI) is a cellular network structure and a Time Division Multiple Access (TDMA) system. For a carrier frequency, the TDMA system will divide a frame into eight time slots, wherein each time slot is used to transmit a channel data for a subscriber. Meanwhile, the General Packet Radio Service (GPRS) technology is one of the available technologies of a GSM system. The GPRS technology utilizes the unused channels in the GSM system to provide moderate speed data transmissions. The Wideband Code Division Multiple Access (W-CDMA) is a wideband spread-spectrum mobile air interface that utilizes the direct-sequence spread spectrum method of asynchronous code division multiple access to achieve higher speeds and support more users when compared to the implementation of time division multiplexing (TDMA) used by GSM systems. Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) is another type of 3G mobile telecommunications standard.
Nowadays, a mobile phone with dual Subscriber Identity Module (SIM) cards is widely used, corresponding to different telephone numbers. The dual SIM mobile phone allows a user to use two communication services without carrying two phones at the same time. For example, the same mobile phone may be used for business and private use with separate numbers and bills. When any SIM card other than the inserted SIM cards required to be used, the mobile phone requires to be powered off to ensure that at least one inserted SIM card can be removed from the mobile phone without any damage. However, the un-removed SIM card lost its connectivity during power off. Additional processing time and power is consumed, as well, for boot-up, public land mobile network (PLMN) search or other requisite initiation procedures for all inserted SIM cards during re-powering on. The similar drawbacks also occur in a mobile phone with a single SIM card socket at the time to replace with another SIM card for use. Therefore, a system for carrying additional subscriber identity cards and capable of communicating with the mobile phone is introduced.